Electron discharge device



2 Sheets-Sheet 2 Filed Sept. 17, 1945 mmm mm mm ATTORNEY I Patented Oct.31, 1950 ELECTRON DISCHARGE DEVICE Charles Norman Smyth, London,England, assignor to Standard Telephones'and Cables Limited, London,England, a British company Application September 17, 1945, Serial No.616,910 In Great Britain May 10, 1945 12 Claims.

The present invention relates to improvements in electron dischargedevices, and is concerned particularly with the design and method ofconstruction of a diode or triode valve adapted for use at ultra highfrequencies.

The dimensions of such valves must be exceedingly small, and it becomesa matter of considerable difiiculty to obtain the interelectrodespacings with the necessary accuracy. It is the principal object of thepresent invention to provide a design which is adaptable for accuratesetting of these spacings.

Valves are now well known in which some or all of the electrodes aremounted on metal discs which are sealed through the walls of theenvelope, which may be of glass or ceramic material. Such discs are usedas the terminals for the corresponding electrodes. A metal disc terminalconsisting of a tubular portion with an outwardly extending flange andsealed at both ends to glass portions of the valve envelope has beendescribed in two patents of C. V. Litton, U. S. Pat. No. 2,336,488,issued December 14, 1943, and U. S. Pat. No. 2,379,584, issued July 3,1945, and modifications of this form are described in C. V.

Littons U. S. Pat. No. 2,309,967, issued February 2, 1943, and his U. S.Pat. No. 2,423,066, issued June 24, 1947, in which the metal terminalisefiectively divided into two portions by a transverse cut through theflange, the envelope being made up by sealing each tubular portion ofthe terminal to the corresponding glass envelope portion and finallyuniting the two metal portions round the flange by soldering or thelike.

None of these arrangements are suitable or convenient when it isnecessary to maintain accurate spacing between the electrodes, and it isthe object of the present invention to provide a construction adaptedfor this purpose. The arrangement according to the invention resemblesthe arrangements covered by the two last mentioned specifications inthat the valve envelope constructed in two or more separate parts eachof which consists of a portion of glass or other insulating materialsealed to a metal portion, two

of the metal portions being finally sealed together; but thecharacteristic feature by which it diifers from all preceding types isthat the two metal portions are both plain discs, not comprising anytubular portions which effectively form part of the envelope.

In the preferred form of the invention the sections of the envelope areconstructed separately, each section being closed at the ends by metaldiscs, one of which carries an electrode and the 2 other has acorresponding central aperture. The" spacing between the electrode ineach section and the outer face of the corresponding apertured disc maybe easily and precisely set in a suitable jig, so" that when theenvelope is completed by sealing the apertured discs together face toface, the desired electrode spacing is automatically obtained withprecision. Where a grid is interposed between the anode and the cathode,this may be sandwiched between the two discs which are sealed together,thereby securing accurate spacing for all the electrodes.

While this type of construction is particularly suitable for miniaturevalves, it is evident that valves of any size may be constructed in thisway.

The invention will be described with reference to the accompanyingdrawings in which- Fig- 1 shows a longitudinal section of a triodevalveaccording to the invention;

Fig. 2 shows an exploded view of some'of theparts of Fig. 1 to show themethod of construction and. to show a slightly modified form of griddiscs;

Figs. 3 and 4 show plan views of two formsof the cathode disc;

Fig. 5 shows the glass stem before sealing on to the remainder of thevalve Fig. 6 shows a plan view of the grid of the valve; and

Fig. '7 shows a partly sectional view of an ultra high frequencyamplifier in which a valve according to the invention is used.

N Fig. 8 is a perspective view of an element of Fig. '7.

An example of a valve in accordance with the invention is shown inFig. 1. It comprises an anode chamber I, a cathode-chamber 2 and a stem-3 attached to the back of the cathode chamber. The anode chamber, alsoseen separately in Fig. 2, comprises a plain flat nickel-iron anode disc4 and an apertured sealing disc 5 of nickeliron having an inwardlybevelled central aperture, both of which discs are sealed by butt sealsto a short length of glass tube 6. The anode l is secured (by coppersoldering, for example) to the disc 4, and may consist of a short lengthof mild steel rod slightly chamfered at one end as indicated'. The outersurface of the disc 5 is ground optically flat and is copper plated.

In order to obtain the necessary accurate spac ing between theelectrodes of the completed valve, the glass sealing of the anodechamber is carried out in a jig which ensures that the distance betweenthe outer surface of the disc 5 and the end surface of the anode l hasaspecified value.

The adjustment of this distance can evidently be;

easily made while the glass is soft, and the adjustment will bemaintained so long as the parts are held in the jig until the glass hasset. The outer surface of the disc is then cleaned and polished andgiven a very thin plated coating of gold, for a reason which will beexplained later on. 1

The cathode chamber consists of a flat nickeliron cathode disc 8, anickel-iron sealing disc 9 of slightly larger diameter than the disc 5,and having a similar inwardly bevelled central aperture. The sealingdiscs 5 and 9 may have corresponding projecting and recessed portionsfor insured registry of the sealing discs. Apertures may becorrespondingly provided in grid 2| to accommodate the projection on oneof the sealing discs. The discs 8 and 9 are sealed by butt seals to ashort length of glass tube ID. The disc 8 has apertures which may bearranged as shown in'Fig-. 3 or Fig. 4. The central circular hole isprovided for the cathode support tube I I, and the other holes areprovided in order to allow passages for exhausting the completedenvelope. The cathode is the upper surface of a cap I2 which slips overthe end of the support tube II. The cathode surface is coated in theusual way with electron emitting material. To the back of the disc .8 issealed the glass stem 3 on which are mounted the leads for the cathodeheater I3 (seen in Fig. 2 only) and for the getter coil I4. The elementsI I and I2 may be of nickel, or preferably of nickel-iron.

The cathode chamber and stem assembly is constructed in the followingway:

The disc 9, glass tube I0, disc 8, and a short piece of glass tubeforming the part I5 of the stem 3, are placed in a jig and heated tomake the metal-to-glass seals. The jig ensures the proper spacing of theparts. The outer surface of the disc 9is then polished and gold flashed,and the upper surface of the cathode disc 8 is also gold flashed.

The next step is to take a glass flared stem tube I6 similar to thatshown in Fig. 5, provided with three lead-out wires IT sealed throughthe fla'reI8 and anchored by a button of glass I9. The cathode heatercoil I3 and getter coil I4 are first'welded on to the three leads asindicated in Fig. 2. The cathode heater coil I3 is passed through thecentral hole in the disc 8 and the flare I8 of the stem tube I 6 issealed on to the end of the glass portion I5 which as already explainedhas been previously sealed to the disc 8.

The cathode cap I2 is next spot welded to the end of the support tubeII, and is then sprayed with electron emitting material. A ring of tinwire 20 is placed around the tube l I and the latter is pushed into thecentral hole of the dis 8, in which it is a tight fit, until the coatedsurface of the cathode cap I2 lies below the upper surface of the disc 9by a specified amount as determined by a suitable gauge, an allowance ofperhaps a few thousandths of an inch being made for expansion.

The next operation is to seal the end of the tube I6 carrying thecathode chamber assembly on to the exhaust pump header. The grid 2|shown in Fig. 6 is laid centrally upon the surface of the disc 9surrounded by a ring of tin wire 22,

and the anode chamber I is laid on top of the grid with the dis 5 insidethe ring of tin wire 22. Ifhe disc 9 is made slightly larger than thedisc 5 sothat the tin ring 22 can be temporarily supported. A suitableclamp is used to hold the chambers I and 2 together in the properposition,

and the assembly is now placed inside the baking oven which has an inertatmosphere. The temperature is raised to about 330 C. with the vacuumpump working, and the tin rings then melt and flow, sealing the cathodesupport tube to the disc 8 and the two discs 5 and 9 together, confiningthe grid 2I between them. It is found that when the tin flows, avacuum-tight seal is formed while the tin is still liquid. Thetemperature can be then raised to 400 C. for baking, and the valve ispumped in the usual way and allowed to cool. The tube is then processed,the getter outgassed and the cathode activated, and sealed 01f. Thegetter is then fired and the getter lead is cut off short.

The grid 2I (Fig. 6) consists of a very thin metal foil having a centralsection 23 perforated with a very fine mesh of holes, say 200 or 300 tothe inch. This grid is preferably produced by a known process in which aformer photographically prepared from a drawing is copper plated,forming a copper grid which can be stripped off, the former being usedagain.

The final operation is to attach a cylindrical metal skirt or sleeve 24by soft soldering to the disc 8, carrying at the lower end an insulatingterminal plate 25 with terminals 26 to which the cathode heater wiresare soldered. The sleeve 24 protects the stem 3 and serves as thecathode terminal. This completes the assembly of the valve. The disc 4forms the anode terminal, and the two discs 5 and 9 together form thegrid terminal.

The gold plating mentioned above is for the purpose of causing themelted tin to run satisfactorily all over the surfaces to be sealed. Ithas been found that the molten tin does not always spread properly overthe copper surfaces to be joined, but a trace of gold on the surfacecompletely removes the trouble. It is therefore only necessary toprovide a very thin coating or flashing of gold on the discs 5, 8 and 9.It has been found unnecessary to gold plate the nickel tube II.

It will be apparent that the method of constructing the valve willensure that the desired electrode spacings are accurately obtained. Itmay be added that in case it is desirable to stretch the grid to ensureits flatness, an annular projecting ridge 56 as shown in Fig. 2 may beformed on the surface of one of the discs 5 or 9 fitting into acorresponding groove 5'! of the other so that the grid will be stretchedtight when the two discs are secured together.

It will be evident also that the grid 2I could be omitted so that thevalve would then be a diode, without any other alteration to the methodof assembly, which would ensure correct spacing between the cathode andthe anode.

It will be noted that the diameters of the discs 4, 5, 9, 8 are inascending order of magnitude. This enables the valve to be insertedanode first into a system of parallel or coaxial screens havingcorresponding apertures in ascending order of magnitude.

A high frequency valve for use at a frequency of several thousandmegacyeles has been constructed in the manner described, of which thediameter over the skirt 25 did not exceed half an inch, the total lengthbeing about one and one eighth inches, excluding the terminal pins 26,the other dimensions being as indicated in Figures 1 to 6, which aredrawn approximately to scale.

Fig. I shows an example of a high frequency amplifying device employingan amplifying Valve according to the invention. It" consists of twocoaxial resonators 21, 28-arranged end to end with a valve 29 similar tothat described with reference to Fig. 1 arranged between them. Thecathode resonator consists of an outer-metal cylindrical tube 30 andan'inner coaxial tube- 3| with an annular sliding piston 32 betweenthem. The tube 3| is'adap'te'd to make contact with the skirt 24 of--the valve 2fi, and holds anfrom by a thin layer 53 of mica or othersuit-- able insulating material. The plug 40 (Fig. 8) has a shallowrecess at the end having a number of slots cut round its periphery toform flexible fingers 58 for grasping the" anode disc of the valve 29.

Sandwiched between the two tubes 30 and 36 is a split metal ring 4|having a circularcentral aperture into which the grid disc 9 of thevalve 29 just fits. This ring is intended to be tightended up by meansof a grub screw at 42 so that it grips the grid disc firmly. The splitring 41 is insulated from both the tubes 30 and 36 by thin mica sheets,or the like 54 and 55.

These tubes are provided with saddles 33 and 44 fixed by metal bandsround the outsides of the tubes and having pegs 45 and 46 running inshort longitudinal guide slots 41 and 48. The saddles carry metal tubes49 and 50 into which coaxial transmission lines are fixed, these linesterminating in coupling loops which project through the slots into thecorresponding resonators. These lines are for the purpose of introducingthe input waves, and extracting the amplified waves, respectively. Thesaddles are adjustable longitudinally to enable the coupling to be madewith suitable parts of the resonators.

When it is desired to extract the valve 29, the grid clamping ring M isloosened and the tube 3| is then withdrawn from the left hand end of thedevice bringing the valve with it.

For operating the device, the high tension supply source 5| is connectedbetween the outer end 52 of the rod 39 and the clamping ring M, asindicated, and a grid bias resistance 52 is connected between theclamping ring 4| and the cathode tube 3|, which is preferably earthed.The necessary decoupling condensers are provided by the mica insulationbetween the clamping ring 4| and the two outer tubes 30 and 36, andbetween the plug 40 and the inner tube 31.

By providing suitable direct coupling (not shown) between the tworesonators, the device may be used as an ultra high frequency generator.

What is claimed is:

1. An electron discharge device comprising an envelope divided into atleast two chambers each consisting of a pair of parallel metal discssealed to the ends of a glass tube, an anode fixed inside one of thechambers to one of the discs thereof, a cathode fixed inside the otherchamher to one of the discs thereof, the other disc of each chamberhaving an aperture opposite the corresponding e1ectrode, said apertureddiscshaving corresponding projecting. and recessed portions to insureregistry of said apertured discs, and the said chambers being securedtogether by a metallic seal between the two apertured discs, one ofwhich is slightly larger'than the other.

2. The method of manufacturing an electron discharge device whichincludes the steps of constructing separately two envelope sections,each section including a portion of insulating material, each sectionalso enclosing and supporting an electrode having a flat operatingsurface; sealing an apertured metal disc to one end of each insulatingportion and with a predetermined spacing between the operating surfaceof the electrodeand the outer surface of the disc; the diameter of thetwo apertured discs being different, winding a piece of solder aroundthe periphery of the larger apertured disc, placing the outer faces ofthe apertured discs of the two sections adjacent one another; anduniting the two envelope sections by melting the winding of solder andallowing it to solidify between the apertured discs.

3. The method of manufacturing an electron discharge device whichincludes the steps of constructing separately each of two; envelopesections by securing an electrode having a flat end face to a flat metaldisc, cutting an aper-' ture in a pair of second fiat metal discs ofdifferent diameters, sealing the said apertured discs respectively tothe ends of a glass tube with the electrode opposite the aperture andwith a specified spacing between the said end'face and the outer surfaceof the apertured disc, and uniting the two envelope sections by windinga piece of solder around the periphery of the larger apertured disc,placing the outer faces of the two apertured discs adjacent one another,melting the winding of solder and allowing it to solidify between theapertured discs.

4. The method according to claim 3 which further comprises placing tinwire around each joint to be soldered, the tin being melted during thebaking process, and gold flashing the surfaces of the discs to be sealedtogether by the tin.

5. The method according to claim 4 which includes the step of grindingflat and polishing the opposing surfaces of the two apertured discs.

6. The method according to claim 2 which further comprises sandwiching agrid electrode between the discs before sealing them together.

7. An ultra high frequency amplifying device comprising an envelopedivided into at least two chambers each consisting of a pair of parallelflat metal discs sealed to the ends of a glass tube, an anode supportedinside one of the chambers on one of the discs thereof, a cathodesupported inside the other chamber on one of the discs thereof, theother disc of each chamber having an aperture opposite the correspondingelectrode, a grid electrode placed between the apertured discs, the saidchambers being aligned with the said apertured discs arranged adjacenteach other and secured together by a metallic seal, a split metal ringadapted to engage said grid discs, a first hollow electric resonatorconnected coaxially between the cathode and the control grid of the saidvalve, a second hollow resonator connected coaxially between the controlgrid and the anode thereof, said hollow resonator comprising outercylindrical members having end portions abutting against said split ringon opposite sides thereof, means for introducing waves to be amplifiedto the first resonator, and means for extracting amplified waves fromthe second resonator.

8. A device according to claim 7 in which the said resonators are of thecoaxial conductor type with means for adjusting the resonance frequencythereof.

9. An electron discharge device comprising an envelope divided into atleast two chambers each consisting of a pair of parallel fiat metaldiscs sealed to the ends of a glass tube, and an anode fixed inside oneof the chambers to one of the discs thereof, a cathode fixed inside theother chamber to one of the discs thereof, the other disc of eachchamber having an aperture opposite the corresponding electrode, ametallic seal between the two apertured discs securing said chamberstogether, one of said discs being slightly larger than the other, asealed-off glass stem sealed to the cathode disc on the side remote fromthe cathode, said cathode disc being perforated to permit a connectionbetween the interior of the stem and the cathode chamber for exhaustpurposes, a hollow indirectly heated cathode having an internal heatercoil whose leads are sealed through said stem, and a tubular metalsleeve surrounding said stem and attached to the cathode disc, saidsleeve also supporting an insulating plate carrying the terminals forsaid heater coil.

10. An electron discharge device comprising an envelope divided into atleast two chambers each consisting of a pair of parallel fiat metaldiscs sealed to the ends of a glass tube, and an anode fixed inside oneof the chambers to one of the discs thereof, a cathode fixed inside theother chamber to one of the discs thereof, the

other disc of each chamber having an aperture opposite the correspondingelectrode, a metallic seal between the two apertured discs securing saidchambers together, one of said discs being slightly larger than theother, a sealed-off glass stem sealed to the cathode disc on the sideremote from the cathode and a tubular metal sleeve surrounding said stemand attached to the cathode disc, said sleeve also supporting aninsulating plate carrying the terminals for said cathode.

11. An electron discharge device according to claim 1 wherein saidprojecting portion of one of said apertured discs constitutes an annularportion and said recessed portion of the other of said apertured discsconstitutes an annular groove accommodating said annular projectingportion to stretch tightly said apertured discs in a plane transverse tothe longitudinal axis of said device.

12. An electron discharge device according to claim 7 wherein saidsecond hollow resonator comprises an inner conductor provided with arecessed metallic plug having flexible fingers engaging said anode disc.

CHARLES NORMAN SMYTH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,367,331 Bondley Jan. 16, 19452,402,601 Chevigny et a1 June 25, 1946 2,404,261 Whinnery July 16, 19462,411,184 Beggs Nov. 19, 1946 2,416,565 Beggs Feb. 25, 1947

